This invention relates to treatment of terminals of a high speed transmission cable used for an electronic computer, etc. and in particular to a method for forming and cutting a flat type multi-core cable, which is necessary for a provisional treatment, when a terminal of the flat type multi-core cable is jointed to a connector or a printed wiring board and to an apparatus for realizing the same.
As prior art techniques concerning the method for forming and cutting a flat type multi-core cable and the apparatus for realizing the same there is known a technique disclosed e.g. in JP (Utility Model)-A-57-192711.
According to this kind of prior art techniques all the core conductors are formed and cut together at an end of the cable by means of a comb-shaped die fabricated so that the pitch thereof is in accordance with the standard pitch of the cable. Consequently, unless errors of the pitch of the core conductors in the cable are smaller than a predetermined value, it is impossible to form them and further this technique is not applicable to a multi-core cable meeting increase of speed and density used in an electronic computer, etc. and to the treatment of a multi-core coaxial cable.
Hereinbelow an example of this kind of prior art techniques will be explained, referring to several figures.
FIG. 1 is a perspective view of a flat type multi-core cable, which is to be formed and cut; FIG. 2 is a perspective view illustrating a form of treatment of the flat type multi-core cable; FIG. 3 is a perspective view for explaining the positioning of the core conductors at a pattern; FIG. 4 is a side view illustrating an apparatus for forming and cutting a flat type multi-core cable according to a prior art technique; and FIG. 5 is a flow chart for explaining the working mode of the apparatus indicated in FIG. 4. In FIGS. 1 to 4 reference numeral 1 represents a flat type multi-core cable; 2 a jacket; 3 exfoliated core conductors; 4 core conductors; 5 signal lines; 6 ground lines; 7 a cross-section of the flat type multi-core cable; 8 a cable clamp for securing the cable 1; 9 cylinders for moving the cable clamp up- and downwards; 10 a uniaxial table; 11 a screw; 12 a step motor; 13 a lumping comb-shaped lower die; 14 a lumping comb-shaped upper die; 15 a transmission type photo-electric sensor; 16 a base plate; 16a a pattern with which the core conductors are to be connected; and 24 a driver.
The flat type multi-core cable 1, which is to be formed and treated, is so constructed that a plurality of core conductors are molded in the jacket 2 so as to be parallel to each other, as indicated in FIG. 1. When a terminal of the core conductors is treated, a part of the jacket 2 in the terminal portion of the flat type multi-core cable 1 so that the core conductors 4 are exposed there in the form of the exfoliated core conductors 3. Each of the core conductors 4 consists of e.g. a signal line 5 and two ground lines 6. However it may be composed of respective one of them. The exfoliated core conductors 3 are formed in the shape indicated in FIG. 2 by means of the forming and cutting apparatus and thereafter they are connected with the connection pattern 16a on the base plate 16, as indicated in FIG. 3.
The forming and cutting apparatus for forming the exfoliated core conductors 3 in the form indicated in FIG. 2 consists of the step motor 12 rotating the screw 11; a uniaxial table 10 movable in the axial direction of the screw 11 by the rotation thereof; a cable clamp 8 disposed on the cylinders 9; a transmission type photoelectric sensor 15; a shape forming die composed of a lumping comb-shaped lower die 13 and a lumping comb-shaped upper die 14; a counter 18 counting detection signals coming from the sensor 15; a pulse generator 20 outputting pulses, depending on the content of the counter 18; and a driver 24 amplifying pulses outputted by the pulse generator 20 and supplying them to the motor 12 so as to drive it. On the uniaxial table 10 there are disposed the shape forming die and the sensor 15 described above movably together with the table 10 so as to be distant from each other by a distance l. Further the table 10 is controlled to be moved by the driver 24 driving the step motor 12, responding to the pulse signal coming from the pulse generator 20.
The operation to form the exfoliated core conductors 3 of the flat type multi-core cable 1 by means of the forming and cutting apparatus thus constructed according to the prior art technique will be explained below, referring to the flow chart indicated in FIG. 5.
(1) The terminal jacket 2 of the flat type multicore cable 1 is removed and the terminal portion of the flat type multi-core cable 1 is secured with the cable clamp 8. Thereafter the shape forming die and the sensor 15 are moved towards the cable clump (Flow 51, 52).
(2) The transmission type photoelectric sensor 15 detects the core conductors 3 of the secured flat multi-core cable 1, when it has reached the position of the cable clamp 8 owing to the movement of the table 10 and gives the counter 18 its detection signals. The counter 18 counts the detection signals and gives the pulse generator 20 an ON signal, when the count has reached a half of the number of the core conductors of the multi-core cable 1, which is previously determined (Flow 53).
(3) When the pulse generator 20 receives the ON signal from the counter 18, it generates a pulse so that the uniaxial table 10 is moved towards the cable clamp 8 further by a distance l between the sensor 15 and the center of the shape forming die from that point of time. Receiving this pulse, the driver 24 drives the step motor 12 so as to move the uniaxial table 10. As the result, the center of the shape forming die consisting of the lumping comb-shaped lower die 13 and the lumping comb-shaped upper die 14 on the uniaxial table 10 is in agreement with the position of the central core conductor 3 in the flat type cable secured by the cable clump 8 (Flow 54).
(4) In this state the shape forming die consisting of the lumping comb-shaped lower die 13 and the lumping comb-shaped upper die 14 is closed and the signal lines 5 and the ground lines 6 of all the core conductors 3 in the flat type cable 1 are formed in a predetermined shape and cut (Flow 55).
(5) After that the shape forming dies 13, 14 are opened and the counter 18 is reset. The uniaxial table 10 is returned to its original position and the cable clamp 8 is loosened. In this way a series of treatments are terminated (Flow 56-59).
As explained above, in the treatment of the core conductors in the flat type cable according to the prior art technique, all the core conductors in the flat type cable are formed simultaneously after having brought the center of the flat type cable so as to be in agreement with the center of the comb-shaped die.
The prior art technique described above has a problem that, in the case where there exist some errors in the pitch of the core conductors because of a restriction in the fabrication of the cable, even if the center of the cable and the center of the shape forming die are in good agreement with each other, outer core conductors of the cable 1 are not always brought on teeth of the shape forming die, which gives rise to impaired core conductors or not well worked core conductors, when the shape forming die is closed. Further the prior art technique has no function to correct the precision of the pitch size between two adjacent core conductors among precisions of the size after the formation of the core conductors. Consequently, since the pitch size after the formation of the core conductors is basically identical to that of the cable itself, when errors in the pitch size of the core conductors exceed a certain threshold value, an imperfectly positioned portion 17 between the pattern 16a and the core conductors arises at the connection thereof with the pattern 16a on the base plate 16. Further the prior art technique has another problem that when two adjacent core conductors are brought close to each other by some cause, before the flat type cable is formed and cut, the sensor cannot distinguish the two core conductors and the counter counts the two core conductors as one, or on the contrary it can happen for one core conductor to be counted as 2 due to vibration, etc. at the movement of the table, which gives rise to another problem that in some cases the central core conductor cannot be brought surely so as to be in agreement with the center position of the shape forming die.